Motility and fertility of frozen bull spermatozoa in tris-yolk and milk extenders containing amikacin sulfate.

Amikacin sulfate, an aminoglycoside antibiotic, effective against some streptomycin-resistant organisms, was tested in bull semen extended with whole milk and egg yolk-Tris extenders in a 6 X 5 X 2 factorial arrangement. Semen from six bulls was frozen in extenders containing 500, 1000, and 2500 microgram/ml of amikacin, a control containing 500 IU/ml of penicillin plus 1000 micrograms/ml of streptomycin plus 500 IU/ml of polymyxin, and control plus amikacin (1000 micrograms/ml). Semen was frozen in .5 ml polyvinyl chloride straws in liquid nitrogen vapor and stored in liquid nitrogen for 2 wk. Straws were thawed in a water bath at 35 degrees C for 30 s. Postthaw motility of spermatozoa in each treatment was assessed using two straws by two observers independently. At amikacin concentrations of 500, 1000, or 2500 micrograms/ml, the percentage of motile spermatozoa averaged 47, 45, and 36% in whole milk and 52, 46, and 46% in egg yolk-Tris. Control and control plus amikacin (1000 micrograms/ml) were 49 and 47% in whole milk and 48 and 52% in egg yolk-Tris. Only amikacin in milk at 2500 micrograms/ml, depressed sperm motility. A fertility trial was conducted to compare the control mixture of antibiotics in whole milk with whole milk also containing 500 micrograms/ml of amikacin. The nonreturn rate to 1182 first service inseminations with semen treated with amikacin (500 micrograms/ml) plus control antibiotics was 70.4% compared with 70.5% for 1494 first service inseminations with control semen. Amikacin can safely be added to whole milk and egg yolk-tris extenders to control streptomycin-resistant organisms.